‘The Line Becomes a River: Dispatches From the...

At age 23, Francisco Cantú suited up in an olive-green uniform and began his first shift as an agent of the United States Border Patrol. It was a curious detour for the young college graduate. “When people ask about you back home and I tell them you’re in law enforcement, they give me the strangest looks,” his mother told him. Cantú himself wasn’t entirely sure about his motivation to join up, only that he had studied international relations and U.S.-Mexico border policy and found the subjects too abstract. He wanted to get right up in the thing itself.

“I don’t know if the border is a place for me to understand myself,” he tells her, “but I know there’s something here that I can’t look away from.”

Cantú would spend four years at the Border Patrol, where he learned to “read the dirt,” as his first supervisor put it, most of the time in a particularly deadly stretch of the Arizona desert. The job caused nightmares, teeth grinding, and nightmares about teeth grinding. (“I dream my molars are falling to pieces, filling my mouth like clumps of hardened dirt.”) It also led to “The Line Becomes a River: Dispatches From the Border,” a book that whips across your face like a sandstorm, embedding bits of the desert into your skin that, like it or not, you’ll carry forward.

The action comes quick. On his second day, they intercept a large load of drugs, though the smugglers get away, leaving behind their backpacks. The agents tear apart the ditched belongings, mostly clothes and food; one man giggles as he urinates on the items. The vast majority of border crossers, of course, are not drug runners but ordinary people looking for work or hoping to join family members up north. When agents discover the possessions of these folks, their response is pretty much the same. They slash the water bottles, stomp on the food, piss all over the clothes.

There is a logic here, if you can locate it among the gratuitous cruelty: Migrants will return to find their supplies gone and head to the nearest road to turn themselves in, perhaps avoiding dangers that lurk deeper in the desert. Cantú tries to believe the logic, but it requires a lack of empathy he can’t sustain. “I have nightmares,” he writes, “visions of them staggering through the desert, men from Michoacán, from places I’ve known, men lost and wandering without food or water, dying slowly as they look for some road, some village, some way out.”

Cantú speaks Spanish and grew up in Arizona; his grandfather came to the United States from Mexico as a child. At work, he tries to comfort apprehended migrants as best he can, plying them with cold bottled water, stopping at McDonald’s to fill them up en route to the station, chatting about their hometowns and probing their reasons for crossing. But they don’t meet him halfway; they can’t. Their lives are in the balance, and this migra agent, nice as he might be, is just background noise to the journeys they desperately need to make. After being fingerprinted, an older man asks if there is any work that needs to be done in the station — perhaps he could take out the trash or clean the cells? “I’m not a bad person,” he tells Cantú. “I want to work.”

If the book ended in 2012, when Cantú left the Border Patrol, it would have been an enlightening but ultimately flawed work. Getting closer to a subject doesn’t always make it clearer, and if there is clarity, it can be the clarity that comes from seeing only a slice of the subject: step to the left or right, and the view dramatically changes. On the job, he sees many migrants but knows none, and they blur together to become yet another abstraction. After talking at relative length with a husband and his pregnant wife, Cantú realizes several hours later that he can no longer even recall their names.

The final and most powerful section of the book occurs away from the border, when Cantú, now a graduate student and coffee barista, befriends José, an undocumented groundskeeper. When José learns that his mother is near death, he leaves his wife and two sons to return to Mexico. He is apprehended while attempting to re-enter the U.S., and the camera swings from the border to the person as the missing details are filled in. There is little about José that is unique: He is a manual laborer, works hard and loves his family. If Cantú had picked him up in the desert, he’s not the kind of person who would have had a particularly heartbreaking story to tell during the drive to the station. He was, in Border Patrol’s vulgar parlance, a POW — a plain old wet.

But Cantú pays attention to the poetry of José’s life in the same way that he pays attention to the poetry of the desert. As he watches the system come crashing down on his friend and does his best to intervene, the scale of the tragedy comes into focus. He hadn’t shared many details about the Border Patrol with his mom, but he can’t keep the story of José from her. “All these years, I told her, it’s like I’ve been circling beneath a giant, my gaze fixed upon its foot resting at the ground,” he writes. “But now, I said, it’s like I’m starting to crane my head upward, like I’m finally seeing the thing that crushes.”

Gabriel Thompson is the author of “America’s Social Arsonist: Fred Ross and Grassroots Organizing in the Twentieth Century” and “Working in the Shadows: A Year of Doing the Jobs (Most) Americans Won’t Do.” Email: books@sfchronicle.com